[Objective] A spill fire can cause considerable property damage and casualties. Although research on spill fires in open spaces is abundant domestically and internationally, research on spill fires in confined spaces is limited. [Methods] To investigate the combustion spread law and temperature field distribution characteristics of spill fires in confined spaces, a 1∶10 reduced-size confined space model was constructed. Seven types of spill fire tests with different mass leakage rates and 12 types of oil pool fire tests with varying sizes were carried out. The analysis focused on the fire source diameter, mass combustion rate, and temperature field distribution characteristics in the confined space. The dimensions of the confined space model were 9 m long, 0.6 m wide, and 0.45 m high. The walls were covered with 2 cm-thick asbestos panels. A fireproof glass with a length of 1 m and a width of 0.45 m was placed horizontally in the center of the model as a spilling burning platform for leaking fuel. The platform was 4 cm away from the bottom of the model. To simulate fuel leakage, a stainless-steel pipe with a diameter of 1 cm was used as a leakage pipe, extending vertically from the ceiling down to the flowing platform. In addition, an electronic balance with an accuracy of 0.1 g was placed under the fuel barrel to measure the fuel leakage rate in real time. [Results] The spill fires in the confined space undergo three stages in accordance with the changes in the fire source diameter over time. These stages are combustion diffusion, stabilization, and extinction. The transition between stages is mainly determined by the relative sizes of the fuel mass leakage rate and mass combustion rate. Equilibrium between the mass combustion rate and mass leakage rate leads to complete fuel combustion before reaching the flame front, the fire source diameter stops increasing, and the combustion enters the stabilization stage. The mass combustion rate of ethanol fuel in a confined space demonstrates a linear correlation with the fire source area because the change in mass combustion rate per unit area exerts less influence on the fuel mass combustion rate than the change in fire source area. During the combustion stabilization, the temperature field distributions of the spill and oil pool fires are similar. The temperature at the root of the fire source gradually decreases as the power of the fire source increases, while the temperature at the top rises continuously. Moreover, the temperature of the ceiling in the confined space increases with the power of the fire source and decreases longitudinally. Finally, a prediction model of ceiling maximum smoke temperature rise during the steady combustion stage of spill and oil pool fires is established. [Conclusions] The findings can provide theoretical support for the detection design of spill fires in confined spaces. © 2024 Tsinghua University. All rights reserved.
